Scientists Develop Better Canine Flu Vaccines

Both humans and animals need proper vaccines to stave off unwanted diseases and viruses. While people have easy access to a flu shot each year to prevent influenza virus, dogs have not had an effective method to prevent canine influenza virus (CIV)—until now.

CIV, or dog flu, is a contagious respiratory disease caused by two strains of influenza.

• H3N2 was adapted from avian influenza virus.
• H3N8 originated from equine influenza virus.

Dogs can suffer from both a mild form of CIV that usually subsides in 2 to 3 weeks or a severe form that is usually accompanied by pneumonia and may prove fatal.

The only currently available vaccines to protect against CIV are inactivated vaccines, and the protection they provide is limited and short-lived.

Using a technique called “reverse genetics,” scientists from the University of Rochester School of Medicine and Dentistry have developed a live-attenuated canine influenza vaccine for use against the H3N8 strain of the virus. The live vaccine replicated in the nose but not in the lungs. The study results showed that the vaccine was safe, more effective than existing vaccines in preventing the H3N8 strain in mice, and provided better immune responses for longer periods of time.

In a second study, some of the same scientists got similar results when they created a second vaccine by removing the NS1 protein in the vaccine. This approach has been used with flu virus vaccines in other species.

Even though these studies proved successful, further studies and development are needed. Clinical trials of both these vaccines in dogs are the next step in development.

The first recognized CIV outbreak in the United States occurred at a greyhound racing track in Florida in January 2004. Since then, the virus has been reported in at least 40 states and Washington, DC, and has affected thousands of dogs. The H3N8 strain is currently circulating among dogs in the United States.

Although there is no evidence to date of CIV being transmitted from dogs to humans, the virus has shown the ability to adapt to different hosts; the H3N2 strain jumped from dogs to cats, and there is evidence that guinea pigs and ferrets can also become infected. Experts say that dogs that have been infected with multiple influenza viruses have the potential to generate strains that could infect people. Therefore, the Centers for Disease Control and Prevention continues to monitor the virus in animal shelters and in homes.